Process of treating ore by flotation



Jan. 22, 1935. w. s. STRINGHAM 1,988,523

PROCESS OF TREATING ORE BY FLOTATION Filed Nv. 6, 1930 ATTORN Patented Jan. 22, 1935 UNITED STATES PATENT oFFicE l 1,988,523 PR'ocEss oF TREATTNG ons BY FLo'rA'rIoN William S. Stringham, Mount Pleasant, Tenn., as-

signor to General Chemical Company, New York, N. Y., a corporation of New York Application November 6, 1930, Serial No. 493,787

11 Claims.

other metals such as copper and zinc.

In several localities there are extensive bodies of iron sulfide ores, generally classed as pyrrhotite, which in addition to iron, contain comparatively small quantities of other metals, notably copper and zinc. Such ore has a high sulfur content, and in many instances, its primary utility is as a source of sulfur in the malng of sulfur dioxide, formed by roasting the-ore in the presence of air or otheroxidizing gas. The sulfur dioxide so obtained is largely employed as such in the arts, and particularly in the manufacture of rsulfuric acid. -The cinder resulting from the roasting operation is substantially free of sulphur, and because of its high iron content is a desirable supply of iron for blast furnace operations directed to the production of pig iron.

When the composition of the cinder from the roasting operation is such that it may be utilized in the manufacture of pig iron, such cinder is a valuable by-product ofthe roasting of the ore,

and is therefore an item of credit which materially reduces the cost of roasting, and the produc tion of the primary product, i. e., the sulfur dioxide.

However, in order that the roasted ore be available for blast furnace operations, it is most desirable that the content of the Icinder of certain other metals, particularly copper and zinc, be verylow, otherwise the cinder may not be used to advantage in a blast furnace. Accordingly, when containing appreciable quantities of copper and zinc, the iron cinder instead of being a source of income in plant operation, becomes an actual additional cost, because of the necessity ofdisposal .in somemanner, of large quantities of useless material.

It so happens that many deposits of iron sulfide include suilicient quantities of metallic impurities, such as copper and zinc, that after the ore is roasted for the sulfur content, the percentage of copper and zinc remaining in the cinder is too high to permit utilization of the cinder in blast furnace operations. As a general rule, it may be said that such impurities are present in the primary sulde ore in comparatively small quantities, frequently about 1% by weight of each, i. e. zinc and copper. -But in spite of this low percentage, the cinder is not generally available for use in the manufacture of pig iron, be-

'cause such cinder should contain a very small percentage of copper and zinc, usually not more than a small fraction of 1% by weight each of copper and zinc.

The principal object of the present invention lies in the provision of a process by means of which large quantities of iron cinder resulting from the roasting of sulfide ores which have heretofore been turned to waste are made available for further use, particularly for the manufacture of iron, thus converting a waste product to one of value. n

The invention includes the reduction of the ore to a suitable pulp and the preliminary conditioning of the pulp to render the vminerals adaptable for flotation; `the separation of micaceous material from the pulp; and the successive concentration and separation from the pulp of copper, zinc, and iron by selective flotation under certain conditions relative to reagents, alkalinity and acidity as hereinafter detailed. Y

The invention may be advantageously described by reference to the accompanying drawing showing a ilow sheet illustrating one preferred method by which the objects of the invention may be effected.

All the separate units of apparatus employed in the present process are of known construction and obtainable in the market. Hence, the ap paratus is indicated diagrammatically on the drawing, and no detailed description 'is given as to the specific construction of the several units.

Referring to the drawing, the numeral 10 indicates a suitable hopper or bin arranged to receive the run-of-mine ore. Ore from the hopper 10 `is conducted to and feo into the crusher 11'by any desirable chutes or other necessary conveyor mechanism. The crushed ore is carried by the elevator or conveyor 12 to the inlet end of the ball mill or other fine grinding unit 13. 'Ifhe discharge endof the ball mill is connected to the inlet of theclassier 14 through the line 15. It will be found that an Akins classifier is well adapted for the purposes of the present process, although any similar device may be employed. The coarser solids in the classier 14 are turned back into the ball mill 13 through the line 16. The pulp of the required degree of fneness is discharged from the classier, and is fed into the conditioning tank 1'( through the line 18.` The conditioning tank 1'7 is simply a large open top tank in which the pulp is retained and agitated fora suilcient period of time to permit the proper conditioning of the pulp for flotation as f ducted through the line 19 into the tank 20. Tank 20 functions similarly to conditioning tank 17, and includes any suitable mechanical means for producing agitation therein so that the pulp may be thoroughly mixed with a frothing agent as will be hereinafter explained. The discharge from the conditioner 20 is fed into the single I cell flotation machine 21 through the line 22.

In the flotation machine 21 micas and related minerals are floated olf from the pulp. The froth from the machine 21 containing principally the mica is passed into the conditioning tank 23 through the line 24. The tails from the machine 21, i. e., the bulk of the pulp including the copper, zinc, iron and other metals, pass through the line 25 into the first cell of a four-cell fiotation machine 26. For the purposes of the present invention the machine 26 may be conveniently designated as a copper rougher.

The flotation machines employed in the present process may be of any suitable type, the Fahrenwald Sub-A and the J anney machines being examples.

The pulp passes successively through the four cells of the rougher 26. The tails froml each cell pass into a succeeding cell, and the copper rougher concentrates are withdrawn from each cell of the rougher and fed into the line 27 through which the copper concentrates are turned back into the line 24, and are thus conducted into the conditioning tank 23 along with the mica froth from the flotation machine 21. The outlet of the conditioner 23 is connected to asimilar conditioning tank 28 by a conduit 29.. The construction of the conditioners 23 and 28 is ysubstantially the same as that of the conditioning tank 17. The discharge from the conditioner 28 passes through the line 30 into the head end of a single cell flotation machine 31, which for the purpose of the present invention may be termed a copper finisher.

tem. The tails from the finisher 31 which include the micaceous material may be disposed of as desired. Alternative methods of disposal of the copper tails will be referred to subsequently.

The tails from the rougher 26 discharged from the last cell thereof are fed into the headA end of the first sell of a three cell flotation machine 35 through the line 36. The froth from each cell of the notation machine 35, constituting the zinc concentrate of the system, is united in the line 37, and conducted to storage. 'Fie tails of each cell of the flotation machine 35 feed into the head of a succeeding cell, and after passing successively through the cells of the machine 35, are discharged into the head end of the first cell of a seven-cell flotation machine indicated gener-l ally at 38.

and the total is combined in the line 40 through The froth from the finisherv 31 constitutes the copper concentrate of the sys- The present process is particularly adaptable for the treatment of a sulfide iron ore containing small quantities of copper and zinc, particularly about or less than 1% by weight of copper and the same relative amount of zinc, the copper and the zinc both being present as sulfides. In order to obtain a roasted iron cinder from the roasting which is salable for use in the manufacture of pig iron, it is desirable to reduce the copper and zinc content of the primary ore to a fraction of 1% by weight, usually to something less than 0.2% or thereabouts.

The pyrrhotite ore treated according to the following description contained 0.46% copper and 0.45% zinc.

'Ihe ore from the hopper l0 is fed into the crusher 11 and broken therein to approximately a 2 inch maximum. The ore thus crushed is conveyed by the elevator 12 to the head end of the ball mill 13. The feed of the ore through the ball mill 13 lis so regulated that the pulp discharged `therefrom through the line l5 contains approximately 60 to 70% solids. Generally speaking, the ore is ground, avoiding sliming as much as practicable, to pass through a standard 48-mesh screen.

During the process reagents are added at several points in the circuit, and the quantities hereinafter referred to in pounds indicate pounds per ton of dry ore.

After the pulp has been fed into the classifier 14, it is treated with 4.5 lbs. of lime to produce an alkalinity in the pulp of approximately pH 9.4. For the treatment ofthe particular ore in question it has been found that an alkalinity approximately as stated affords most satisfactory results. However, the alkalinity of the pulp may range from about pH 8 to about pH 10 according to the nature of the ore being treated. About 0.15 lbs. of thiocarbanilid is fed into the classifier 14, and mixed with the ore therein during the classification. Thev thiocarbanilid serves chiefly as an activating agent, and thus facilitates subsequent flotation of the floatable substances. The lime and thiocarbanilid are both added to the pulp while the latter is in the classifier so as to effect a thorough mixture o f these substances with the pulp. I'he classifier 14 is operated in such a manner, as is well known in the art, that the pulp discharged therefrom into the conditioner 17 contains approximately 35% solids. Coarser material passes back to the ball mill 13 through the line 16.

The conditioners 17 and 20 are together of such size and capacity that during the passage of the pulp through these tanks a sufficient period of time elapses to permit the ore to be brought into proper condition for flotation.

In the tank 20 approximately 0.2 lb. of pine oil or other suitable frothing agent is added to the pulp. During passage of the pulp through the tank 20, the agitating mechanism therein is operated sufficiently to afford a thorough mixing of the pulp and the frothing agent. As the pulp leaves the conditioner 20, the percentage of solids will have been reduced to approximately 27%, and at this degree of concentration, the pulp is fed into the head end of the single cell flotation machine 21. In the flotation machine 21, the mica is floated away from the pulp, and the mica froth passes out of the machine as the heads through the line 24 and into the conditioner 23.

The tails from the machine 21 comprise the main body of the pulp and include substantially all the iron and zinc, and the greater part of the upper. The pulp is tnen'red into the head ena of the first cell of the copper rougher 26 through the line 25. At this point in the circuit about 0.002 lb. of pine oil and 0.007 lb. of sodium xanthate are added to the pulp. By the time the pulp reaches the head end of the first cell of the rougher 26, the alkalinity has been reduced to about pH 9.0 which is a suitable degree of alkalinity for selective flotation of the chalcopyrite. Here again the alkalinity of the circuit depends more or less upon the ore being treated, and it has been found that in some instances the alkalinity may vary. between about pH 8 and pH 10. It has also been found that potassium xanthate and phosphocresylic acid may be employed as collecting agents at this stage of the process.

In the rougher 26 copper sulde is concentrated in the copper-bearing froth. The froth is withdrawn from each cell and fed into the line 27.

The alkalinity lof the rougher concentrate is Isomewhat lower than desirable for the succeeding treatment of the copper concentrate. Accordin'gly, about 0.5 lb. of lime is introduced into the copper concentrate circuit in the line 27. The

copper concentrate passes from line 27 into the line 24 and becomes mixed therein with the mica froth from the fiotation machine 21. The mixture of mica and copper concentrate is passed successively through the conditioners 23 and 28. The time of passage of the pulp through these tanks isv so regulated as to place the mixture in condition for final concentration of' the copper. After proper conditioning, the pulp from the conditioner 28 is conducted into the head end of the copper finishing notation machine 31 through the line 30. 'I'he alkalinity of the copper concentrate circuit in the line 30 -is about pH 9.4. This value may vary according to the ore being treated between about pH 8 and pH 10.

On the introduction of the pulp into the 15in-l isher 3l, a further addition of'frothing and otation agents is made. Pine oil and xanthate respectively are suitable, and these substances may be addedin quantities corresponding to those introduced into theY first cell of `the rougher 26.l In some instances; itvmay be unnecessary to introduce into the finisher 31 quite such large amounts of frothing and flotation agents as are introduced into' the head end of the rst cell of the rougher 26. The exact quantities of reagents to be introduced into the finisher are more or less controlled by specic 'operating conditions. In

,the nishing machine 31, the copper sulfide is Y subjectedtoa final' concentration,l and a froth high in copper and containing most of the copper of the original ore is drawn off from the cell as a copper concentrate and as one product 'of the process.

It has been found in many cases that the mica froth withdrawn from the machine 21V contains` appreciable quantities of copper, in some instances about 2% It would be generally desirable to save as much of this copper as possible, and for this reason the mica froth is sent through the conditioners 23 and 28, and then into the finisher 31-r to recover as much copper as possible from the mica froth. The tails from the finisher 31 include the mica. The copper tails may be sent to waste, or may be turned back into the heads of the copper rougher 26. If the latter procedure is adopted, it will be apparent that the mica will go on throughV the circuit, and finally appear in the tails of the last machine 38.

The tails ofthe last cell of the rougher 26 include the ircn and the zinc. The percentage 'of solids in the system hasby this time` been reduced `to about 25%. Prior to the introduction of the tails from the rougher 26 into the head end of the first cell of the zinc concentrating machine 35 about 0.6 lb. of copper sulfate, about 0.1 lb.-

of a creosote oil collecting agent known as 634 Barrett fiotation agent, about 0.05 lb. pine oil and approximately 0.07 1b. of sodium xanthate are added to the circuit. The function of the copper sulfate is chiefiy as an activating agent serving to activate the sphalerite, so as to render the same fioatable in the concentrator 35. The

creosote oil collecting agent is'prim'arily a collecting or flotation agent for zinc, but vadditionally has some activating properties. The sodium xan# thate acts as a flotation agent, and the function of the pine oil' is that of a frothing agent. Potassium xanthate or phosphocresylic acid may also be employed as flotation agents. As the pulp passes successively through the several cells of the flotation machine 35, a froth high in zinc is formed in each cell. The zinc froth is withdrawn from each cell and fed into the line 37 through which the zinc concentrates are conducted to storage. Asthe pulp passes through the copper rougher 26 and through the zinc concentrator 35,

the alkalinity is gradually reduced until by the time the pulp is discharged from theI last cell of the concentrator 35, a substantially-neutral condition is attained.

The tails from the zinc concentrator 35 `are fed into the head end of the first cell of the flotation machine 38. About 1.4 lbs. of crude oil, for example Mexican fuel oil, about 0.4 lb. cresylic acid and about 235 lbs. sulfuric'acid are introduced into the head `end Vof the first cell of the iron concentrator 38. During the passage of the pulp through the iron concentrator 38 about 0.95 lb. of gasolene is added to the mixture in order to somewhat dilute the crude oil. The acid is added `at the head of the first cell of the iron concentrator to render the pulp slightly acid so as to facilitate the flotation of the iron. Up to Athis point the circuit has been preferably mainnot essential that the circuit be acid at this point, but such is desirable. The pH value in the circuit at the head end of the first cellrof the concentrator 38 may varyfrom 6.5 to 7.5 according to the ore -being treated and the specific operating conditions. The crude oil and the cresylic acid are probably primarily frothing agents, but may additionally have some ac'k tivating properties. About 0.06,.lb. of sodium xanthate is added to the circuit during the passage of the pulp through the machine 38.

Potassium xanthate or phosphocresylicacid may also be employed. The addition of the flotation agent may be made in any one or more of the cells near the-head of the machine, but it is preferable to avoid addition of the xanthate in the first cell of the unit so as to permit the firstv cell to act somewhat as a conditioner.

During the passage of the pulp through the concentrator 38, a froth high in iron is formed..

in each celland withdrawn therefrom and fed into the line 40. The tails from the concentrator 38 are turned to waste through the line 39. The iron sulfide concentrate from the line 40 may be dried and suitably conditioned for roasting.

The iron concentrate .may be roasted in any suitable manner in the presence of air or other oxidizing gas to produce sulfur dioxide which may be utilized as desired. If the roasting operation per se is such as to produce a more or less granular cinder, it is generally desirable to subject such cinder to a slight sintering to improve its mechanical condition for handling. 'Ihe roasted concentrate is substantially free of sulfur, consists almost entirely of oxide of iron (analyzing somewhat over -60% metallic iron) and contains an extremelyrsmall quantity of copper and zinc as impurities. Such product is particularly satisfactory and desirable for utilization in blast furnace operations for the production of pig iron. n

In the appended claims the expressions high in copper, high in zinc, and high in iron are intended to indicate a condition in which the froth referred to contains the metal named in comparatively large quantities with respect to the amount of either of the other principal metals contained in the same froth or concentrate.

I claim:

1. The process of treating a sulfide ore predominating in iron and containing comparatively small quantities of copper and zinc to produce an iron concentrate low in copper and zinc which comprises agitating a pulp of the ore having an alkalinity substantially within the pH range of 8 to 10 with a xanthate and a frothing agent to form a mineral-bearingfroth high in copper, separating the froth, agitating the pulp while maintaining the same in a less alkaline condition with a collecting agent and a frothing agent to form a mineral-bearing froth high in zinc, separating the froth, acidifying the pulp, further agitating the pulp with a xanthate and a frothing agentv to form a froth high in iron, and separating the last mentioned froth from the pulp.

2. The process of treating a sulde ore predominating in iron and containing comparatively small quantities of copper and zinc, and a quantity of micaceous` material to produce an iron concentrate which comprises agitating an alkaline pulp of the ore and a frothing agent to form a froth containing micaceous material, separating the mica froth, agitating the pulp with a xanthate and a frothing agent to form a mineral-bearing froth high in' copper, separating the froth, further treating the copper froth and the micaceous froth with additional collecting agent and frothing agent to produce a copper concentrate, agitating the pulp with a collecting agent, an activating agent, and a frothing agentto form a mineral-bearing froth high adapted after roasting for the commercial production of metallic iron.

3. The process of treating a sulfide ore predominating in iron and containing comparatively small quantities of copper and zincto vproduce an iron concentrate low in copper and zincwhich comprises vagitating an yalkaline pulp of the ore with a xanthate and a frothing agent `to form a mineral-bearing froth high incopper,

separating the froth, Vagitating the pulp with a collecting` agent,l an activating agent, and a frothing agent to form a mineral-bearing froth high in zinc, separating `the froth, acidifying the pulp, further agitating the pulp with a xanthate and a frothing agent to form a froth high in iron, and separating the last mentioned froth from the pulp, whereby an iron concentrate is produced substantially freeof copper and zinc.

4. The process of treating a sulfide ore predominating in iron and containing comparatively small quantities of copper and zinc, and a quantity of micaceous material to produce an iron concentrate which comprises agitating a pulp of the ore and an oily frothing agent to form a froth containing micaceous material, separating the micaceous froth, agitating the-pulp with a collecting agent and a frothing agent to form a mineral-bearing froth highv in copper, separating the froth, agitating the pulp with a collecting agent and a frothing agent to form a mineral-bearing froth high in zinc, separating the froth,-and further agitating the pulp with a collecting agent and a frothing agent to form' a froth high in iron, and separating the last mentioned froth from the pulp,l whereby an iron concentrate is produced substantially vfree yof copper and zinc.

5. The process of treating a sulfide ore containing copper, zinc, iron, and micaceous material to produce an iron concentrate which comprises agitating a pulp of the ore and an oily frothing agent to form a froth containing micaceous material, separating the micaceous froth, agitating the pulp with a collecting agent and a frothing agent to form aI mineral-bearing froth high in copper, separating the froth, further treating the copper froth with additional collectingA agent and frothing agent to produce a copper concentrate, agitating the pulp with a collecting agent and a frothingagent to form a mineral-bearing froth high in zinc, separating the froth, and further agitating the pulp with a collecting agent andA a frothing agent to form a froth high in iron, and separating vthe last mentioned froth from the pulp.

6. 'Ihe process of treating a sulfide ore containing copper, zinc, iron, and micaceous material to produce an iron concentrate which comprises agitating an alkaline pulp of the ore and an oily frothing agent to form a froth containing micaceous material, separating the mica-bearing froth, agitating the pulp with a xanthate and a frothing agent to form a mineral-bearing froth high in copper, separating the froth, further treating the copper froth and the micaceous froth with additional collecting agent and frothing agent to produce a copper concentrate, agitating the pulp with`a collecting agent and a frothing agent to form a mineral-bearing froth high in zinc, separating the froth, acidifying the pulp, further agitating the pulp with a xanthateand a frothing agent to form a froth high in iron, and separating the last mentioned froth from the pulp. A' 7. The process vof treating a sulfide ore containing'copper, zinc, iron, and micaceous material to produce an iron concentrate which comprises agitating the/pulp ofthe ore andan oily frothing agent to form a froth 'containing micaceous-material, lseparating the mica-bearing froth, agitating the pulp with fa Xanthate and afrothing agent'to form a mineral-bearing froth high in copper, separating the froth;

further treating the copper 'froth and the and frothing agent to produce'a 'copper concenvlo trate, agitating the pulp with a collecting agentand a frothing agent to form a mineral-bearing froth high in zinc, separating the froth, and further agitating the pulp with a xanthate and a frothing agent to form a froth high in iron, and separating the last mentioned froth from the pulp. A

8. 'Ihe process of treating a sulde ore containing copper, zinc, iron, and micaceous material to produce an ironconcentrate which comprises agitating the pulp of the ore and an oily frothing agent to form a -froth containing micaceous material, separating the mica-bearing froth, agitating the pulp with a collecting agent and a. frothing agent to form a mineralbearing froth high in copper, separating the froth, further treating the copper froth and the micaceous froth with additional collecting agent and frothing agent to produce a copper concentrate, agitating the pulp with a collecting agent and a frothing agent to form a mineralbearing froth high in zinc, separating the froth, and further agitating the pulp with a collecting agent and a frothing agent to form a froth high in iron, and separating the last-mentioned froth from the pulp.

9. The process of treating a sulfide ore containing copper, zinc, iron, and micaceous material to produce an iron concentrate which comprises agitating an alkaline pulp of the ore and an oily frothingagent to form a froth containing micaceous material, separating the mica-bearing froth, agitating the pulp with a collecting agent and a frothing agent to form a mineralbearing froth high in copper, separating the froth, further treating the copper froth with additional collecting agent and frothing agent tok produce a copper concentrate, agitating the pulp with a collecting agent and a frothing agent to form a mineral-bearing froth high in zinc, separating the froth, acidifying the pulp, further agitating the pulp with a collecting agent and a lfrothing agent while `less alkaline condition to form a mineral-bearing iron concentrate which comprises agitating an alkaline pulp of the ore and an oily frothing agent to form a froth containing micaceous material, separating the mica froth, agitating the pulp with a xanthate and a frothing agent to form a mineral-bearing froth high in copper,

separating the froth, agitating the pulp with a` collecting agent, an activating agent, and a maintaining the pulp in a froth high in zinc, separating the froth, acidifying the pulp, further agitating the pulp with a xanthate and a frothing agent to form a froth high in iron and separating the last mentioned froth from the pulp, whereby an iron concentrate is produced substantially free of copper and zinc and adapted after roasting for the commercial production of metallic iron.

11. The process of treating a sulde ore predominating in iron and containing comparatively small-quantities of copper and zinc to produce an iron concentrate low in copper and zinc which comprises agitating an alkaline pulp of the ore with a xanthate and a frothing agent to form a mineral-bearing froth high in copper, separating the froth, agitating the pulp with a collecting .agent and a frothing agent toform a mineralbearing froth high in zinc, separating the froth, acidifying the pulp, further agitating the pulp with a xanthate and a frothing agent to form a froth high in iron, and separating the last mentioned froth from the pulp, whereby an iron concentrate is produced substantially free of copper and zinc.

WILLIAM S. STRINGHAM. 

